We propose to investigate the use of artificial lipid bilayer particles, liposomes, as vectors for introducing biologically-active materials into tumor cells. Liposomes are prepared from various purified and chemically defined lipids, phospholids and cholesterol, or from the lipids extracted from autologous organs or cells of the host. In addition, we prepare glycoproteins and glycolipids from various target tissues, such as lung, mammary, liver, and prostate carcinoma. These preparations are incorporated into the liposomes and tested for efficiency of fusion preferentially with the desirable target organs and with the malignant cells. Various chemotherapeutic agents such as methotrexate, Ara-C, 5-fluorouracil or new agents are encapsulated and tested for the efficiency in delivering them with liposomes. In addition, liposomes containing the active poly-phosphorylated forms of antimetabolites are used in efforts to circumvent drug resistance resulting from diminished intracellular net phosphorylation rates. The results of this study will contribute to the development of improved therapeutic approaches and to the possible solution of drug resistance in neoplasia.